Undercarriage for aeroplanes



June 11, 1929. w. E. GRAY 1,716,439

UNDERCARRIAGE FOR AEROPLANES Filed Oct. 14, 1927 2 Sheets-Shet 1 June 11, 1929. w. E. GRAY UNDERCARRIAGE FOR AEROPLANES 2 Sheets-Sheet 2 Filed Oct. 14, 1927 Patented June 11, 1929.

UNITED- STATES 1,716,439 PATENT oFFlcE.

WILLIAM EDRINGTON GRAY, OF LONDON,

'UNDERCARRLAGE FOR AEROPLANES.

Application filed October 14, 1927, Serial No. 226,241, and in Great Britain- October a5, 1826.

This invention relates to undercarriages for aeroplanes in which the weight of the machine is supported while on the ground by two sets of wheels, one set ahead of the centre of gravity of the machine, and the other at the rear thereof.

It has heretofore been proposed to provide such an undercarriage with means for raising and lowering one of the sets of wheels during flight, and also with means for steering the machine but a large angle of attack of the main planes was relied on for stopping the machine when landing.

This invention has for its main object to enable a machine to take-ofi from wheels on the ground and with the main planes of the machine at a large angle of attack, and then while in the air to so alter the position of at least one of the sets of wheels that on touching the ground in landing the rear set shall touch first and thus automatically tip the machine forward on to the front set also, and thus reduce the angle of attack of the main planes, so that the weight is transferred from the planes to the wheels, thus enabling the machine to be brought to rest quickly by applying brakes to the wheels.

Another object of the invention is to render it possible to land an aeroplane on steerable wheels in a restricted space either at stalling speed or at a much higher speed if necessary, and yet come to rest quickly.

A further object of the invention is to lessen the risk of the machine provided with an undercarriage of the type described from leaving the ground again accidentally when landing, as compared with present day prae-.

tice.

According to the invention, there is provided an undercarriage for aeroplanes comprising two sets of wheels, one ahead and the other at the rear of the centre of gravity of the machine, at least one of which sets of wheels is capable of steering the machine while on the ground, at least one of said sets of wheels is fitted with braking mechanism, and at least on of said sets is capable of being raised and lowered while in the air and capable of supporting the machine both while in the raised and lowered positions, for the purposes set forth above.

According to another feature of the invention, the set of wheels which can be raised and lowered while in the air can be mechanically fixed in its position of adjustment so as to relieve ;the pilot of the weight of the machine durihg the entire taking-off operation. It

According to a further feature of the invention, the set of wheels that can be raised and lowered when in the air is so operatively connected with the rudder'eontrol of the machme that the same. set of wheels'can be steered with the rudder in all positions of ad ustment of the set of wheels.

The, term set' of wheels used in this specificatlon and in the claims is to be understood as covering either one or more wheels. One set of-wheels, for example the rear set, is preferably composed of at least two wheels having a wide track, and the other set, for example the front set, may have only one wheel, but if it has more than one wheel the track is preferably wide also. A set of wheels may consist of any number of wheels, but their axes should lie in one transverse vertical plane. Both sets of wheels may be adjustable in height. The

angle of attack in the landing position may -be negative. All the wheels in a set are preferably adjusted together, and all the wheels of a set preferably have the same de- The front set of wheels is preferably situated far enough ahead of the centre of gravity of the machine to avoid risk of overturning and to allow the rear set to carry a large part of the weight. The rear set is preferably situated only a short'distance to the rear. of the vertical plane passing through the centre of gravity of the machine in order to take a large part of the weight of the machine, but far enough back to prevent the machine from upsetting backwards. I

All the wheels are preferably supported by any convenient type of shock-absorbing devices, preferably with energy-dissipating means associated therewith. The vertical movement permitted to the wheels by such devices is in addition to the vertical adjustment of the wheels according to this invention.

The two sets of wheels are normally the only parts of the machine to touch the ground, but skids may be provided to' protect the wing tips or tail in emergency. Such skids, if provided, however, should not contact with the ground and exercise a braking action on the machine when taking off.

The invention consists in the construction, arrangement and combination of parts described hereinafter and pointed out in the claims.

In order that the invention may be clearly understood reference will be made to the accompanying drawing wherein one embodiment is diagrammatically illustrated by way of example. In said drawing Figure 1 is a diagrammatic side elevation, partly in section, showing an aeroplane pro vided with an under-carriage according to the invention, some parts, including one rear wheel, being omitted for the sake of clearness;

Figure 2 is a undercarriage Figure 3 is a diagrammatic plan view of the steering mechanism;

Figure 4 is a sectional side elevation of the front wheel mounting and steering mech anism;

Figure 5 is a vertical section showing details of the upper bearing of the front wheel tube, and

Figure 6 is a side elevation of the rear wheel and its braking mechanism shown in Figure 2.

Like reference characters designate like parts throughout the several views.

Referring to the drawing, the undercarriage illustrated comprises a front set of wheels consisting of only one wheel and it is given the properties of steering and posi-' tion adjustment, while the rear set consists of two wheels to which brakes are fitted.

As shown in Figures 1 and 2, the rear wheels 1 having brakes 2 are carried on axles 3 and supported by radius members 4 to which the brakes are anchored, and by shockabsorbing members 5 of any convenient type. The members 3, 4 and 5 are pivoted to the main plane 6 at points 7, 8 and 9, respectively. The front wheel 10 is carried in a fork 11 on a tube 12 constituting a steering column which is supported by cross members 13, 14 of the frameat situations 15 and 16. The ground line corresponding to the landing position is shown at 17 The front wheel 10 is capable of being lowered, as described hereinafter, to the position indicated by broken lines 18 for taking-off, and the ground line is then at 19 as indicated by the broken line. The centre of gravity of the machine is at 20, and 21 indicates a partial front elevation of the Figure 3, is so pivotally connected with an upstanding tubular member 27 that it can swil'ig about the same and also move endwise along it. The tube 27 is rigidly connected at its ends to arms 28 which are fast on the opposite ends of an upstanding tube 29 that carries a rudder bar 30, the tube 29 being journalled in upper and lower frame cross members 31 and 32 respectively. The rudder bar thus controls the front wheel for steering.

The upper part of the steering column or tube 12 is carried in a screwthreaded tube 33, on the lower end of which is fastened a collar 34 having an arm 35 pivotally and slidably connected with the tube 27. Between the collars 25 and 34 is a-spring36 which carries the load of the front wheel and is damped by a shock-absorber 37 pivoted to the collars 25 and 34.

As shown in Figure 5, the screwthreaded tube 33 is supported by a nut 38 in the form of a sprocket-wheel. This nut is arranged in a two-part bush 39 carried between a hemispherical housing 40 fixed to the cross member 14, and a rubber pad 41 on the latter. A ball-bearing is inserted between the top of the nut 38 and the bush 39 for reducing friction. The nut 38 has teeth on its outer periphery and can be rotated while in the air by a chain 48 (Figure 4) which passes through openings in the parts 39, 40 and round a wheel 43 which can be turned by a handle 44. A screw 45 locates the bush 39 in the housing 40 within small limits. A spring 46 is interposed between the upper end of the screwthreaded tube 33 and a collar 47 fast on the top of the steering column 12. By rotating the handle 44 the airman can raise or lower the front wheel 10 which is always capable of steering and supporting the machine. In any position of adjustment of the wheel 10 it is mechan ically held against up and down movement, so that the airman has not to take the weight of the machine during any operation.

Any convenient braking mechanism may be employed. As shown. in Figures 2 and 6, a lever 50 for actuating the expanding member of an expanding brake 2is attached to one end of a Bowden wire 51 that is anchored at 52 and has its other end operable by a lever 53 within reach of the pilot.

It will be appreciated that the construction of aeroplane undercarriage described above enables the machine to take-off from wheels on the ground with the main planes at a large angle ofattack, whereupon the pilot when in the air can so alter the position of the front wheel that on touching the ground, when landing either at or abovestalling speed, the rear wheels touch first, when the machine will automatically tip forward and rest on the front wheel, the angle of attack of the main planes being thereby reduced so that the weight is transferred from the-planes to the wheels, when the machine can be rapidly brought to rest in a restricted space either at stalling speed, or at a considerably higher speed by applying the brakes to the rear wheels. There is consequently very little risk of the machine leaving the ground again accidentally when landing after one or more wheels have made contact with the ground.

I claim:

1. An undercarriage for aeroplanes comprising in combination two sets of wheels (each set consisting of one or more wheels), one set ahead of and the other set at the rear of the vertical plane passing through the centre of gravity of the machine, which sets of wheels normally support the whole ground-borne weight of the machine in taking-off and in landing, mechanism to enable an occupant of the machine while in the air to alter the position of at least one of the said sets of wheels so that on landing the angle of attack of the main planes is less than it was when taking-off, mechanism to enable at least one of the said sets of wheels to be operated for steering the machine, and braking mechanism acting on at least one of the said sets of wheels, the front set of wheels being situated far enough ahead of said vertical plane through the centre of gravity of the machine to avoid risk of overturning and to allow the rear set of wheels to carry a large part of the ground-borne weight of the machine for the purpose described.

2. In an aeroplane, the combination with the frame, of two sets of wheels, one situated ahead and the other at the rear of the vertical plane passing through the centre of gravity of the machine, which sets are intended normally to support the whole ground-borne weight of the machine in taking-oil and in landing, means operable by a person in the machine while in the air for raising and lowering one of said sets of wheels and mechanically holding the same in its position of adjustment so as, when on the ground, to be capable of supporting the machine while in the raised or lowered position independently of the operator, and so that on landing the angle of attack of the main planes is less than it was when takingoif, means for so operating at least one of the vertical plane passing through the centre 7 of gravity of the machine, which sets are intended normall to support the whole ground-borne weight of the machine in taking-off and in landing, means operable by a person in the machine while in, the air and arranged to raise and lower the front set of wheels so that on landing the angle of attack of the main planes shall be less than it was when taking-off, means for so operating at least one of the said sets of wheels as to steer the machine when on the ground, and braking mechanism applied to the rear set of wheels and operable from the machine, for the purpose described.

4. In an aeroplane, the combination with the frame, of two sets of wheels, one set situated ahead and the other at the rear of the vertical plane passing through the centre of gravity of the machine, which sets are intended normally to support the whole" ground-borne weight of the machine in taking-oft and in landing, a rudder bar mounted to rock about an upstanding axis, mechanism operable by a person in the machine for raising and lowering one set of wheels in relation to the main planes while in the air, so that on landing the angle of attack of the main planes is less than it was when taking-off, means operatively connecting the rudder bar with said mechanism in all positions of the set of wheels controlled by the latter, so that the movements of the rudder bar are imparted to the steeredset of wheels in all positions of adjustment of the latter, and braking mechanism applied to at least one of the said sets of wheels and operable from the machine, for the purpose described.

5. In an aeroplane, the combination with the frame, of two sets of wheels, one set situated ahead and the other at the rear of the vertical plane passing through the centre of gravity of the machine, which sets are intended normally to support the whole ground-borne weight of the machine in taking-oil and in landing, a rudder bar mounted in the frame to rock about an upstanding axis, mechanism operable bya person in the machine for raising and lowering wheels, means for moving the' steering standing axis and pivotally engaged by the column endwise in the frame and holding other end of said arm, which latter is mov- 10 it mechanically against endwise movement able along the said upstandin member, and in its position of adjustment, an arm that a brake that is applied to the rear set of 5 has one end fast on the steering column and wheels and is operable from the machine,

extends transversely of the length of the for the purpose described.

latter, and an upstandin member mounted In testimony whereof I afiix my signature. to rock with the rudder ar about said up- WILLIAM'EDRINGTON GRAY.. 

